Samsung WD80N645OOW died mid-cycle

[CapLeaker]

Keep on digging and restore VCC. Maybe a bad startup resistor gone high in value or some thing along these lines. Without proper VCC it's not going to work. So this is priority. What is the part number of the pwm?

[mrsith]

Cant edit for the fifth time lol. DC volts on bridge rectifier initially jumped above 20v, then strarted decreasing. Unplugged and plugged back in when dropped under 10v, it raised to just around 11.5v and started to drop after a few seconds.

[mrsith]

I've seen another thread on this forum, where someone had faulty voltage regulator (KIAsomething I think). It worked fine only if heated up, wasn't completely dead, like a zombie ic lol. Maybe something similar happens here?

Otherwise, what might be telling it to shut down? I'd consider just buying a new board if I was sure it'll work well lol. Getting desperate with laundry 🙃

Edit: when I think about it, isn't that the standby voltage that's wrong here? I mean this is required to power the sub pcb, which includes power button to run main relay.

Edit2: this 7-legged wonder description: "Including an auto standby function in the controller, the product achieves the low standby power by the automatic switching between the PWM operation in normal operation and the burst-oscillation under light load conditions." It also features protections:

　Overcurrent Protection (OCP) : Pulse-by-Pulse
　Overload Protection (OLP) : auto-restart
　Overvoltage Protection (OVP) : auto-restart
　Thermal Shutdown Protection (TSD) : auto-restart

According to datasheet it oscillated at 62khz, so it's not what I'm reading. Auto-restarting or pulse-by-pulse protecting?

Even another edit: measured Vcc pin voltage, at the beginning it was jumping between 18.something volts and 0, quite rapidly, after a while It was just over 2 volts. The initial jumping might've been caused by me trying to pry the probes through the resin though.
According to datsheet, it requires 15.3v to start. I need to figure out if it fails because of something else or itself.

Edit spree (still better than multiposting): checked ac voltage on middle pins of bridge rectifier (the large one just behind the fuse that was blowing), getting very small voltage (8-20), with occasional split second very high spikes.

Is there something else other than the rectifier itself that could cause this?

[CapLeaker]

Well, at least you found something is a miss. Something is telling the pwm to shut down. It's still alive, other than that you wouldn't get anything at all.

[mrsith]

I have noticed that without the CN7 plugged in (front panel + inverter communication pins) the led on the main board blinks repeatedly.

Checked DC voltages there, instead of 5v I have unstable reading (jumping from 0-2.5v-0-3.2v-0-4.2v-0 etc, doesn't reach 5v), on 12v pin I'm getting 10-11.5v, randomly fluctuating.

[CapLeaker]

Hmm. So you got power going to, but nothing coming out of the board and the machine is absolutely dead? Mabe the STBY power is fuxed. I mean of these power supplies gotta be on 24/7. Also check larger wattage power resistors (SMD) they can unsolder themselves one side from the board. Filter inductors in the primary is another hidden spot. Transformers where the wire broke off at the leg, A fusible resistor, PWM, or a short on the secondary. Oh! Maybe it’s one of the safety crap sensors! Sorry… still early here a working on downing my coffee!

[mrsith]

Fuse on the other board is fine. Your favourite kind of ic seems good too. I'm running out of ideas.

Just ckecked main relay with service psu, works fine.

[CapLeaker]

It could be that finally one of my favourite power IC’s blew too.

[mrsith]

I will check it in the morning. I don't understand why would it blow, if the washing machine was powering up with faulty pump and only blew a fuse when intended to use it, why would another fuse, on a different board, blow with new pump installed? Machine newer powered up or clicked any relay even once after I put it back together. It was continuously clicking the relay before replacing the pump along with the fuse.

I need some sleep, cannot think even remotely clear anymore lol.

[CapLeaker]

Wasn’t there another white glass fuse somwhere on the boards?

[mrsith]

Replaced the pump, the fuse again, but I have a suty no power now. Nothing clicks, no leds go up, absolutely nothing. Checked main fuse again, confirmed with dmm that there's continuity between the mains plug and the main board connectors. Can't see any shorts etc either.

[sam_sam_sam]

put a lamp in series with the pump and see if the fuse doesnt blow

I would add one thing to this is dose the pump runs or is the light very bright if this could be your problem with the motor

[stj]

put a lamp in series with the pump and see if the fuse doesnt blow

[mrsith]

Took the pumps out, checked their resistances by inserting probes into the connector. One pump (I think the drain one) measures 190.5 ohms which I think is good, the other (circulation pump?), the one that the sock was in, has just 11.8 ohms.

So I guess I should replace the circulation pump. And the fuse, of course.

[mrsith]

Yeah, acting exactly the same. I'm steering toward the drain pump because of that sock that was stuck inside, but need to take it out to check resistance to be sure.

[CapLeaker]

Fuse blown again?

[mrsith]

Started a program, machine took some water in and died shortly, everything took maybe 2 minutes. No water drained out. But that early within the program, would drain pump even try to start? Maybe it's the motor that died?

[CapLeaker]

awesome!

[mrsith]

Okay.

Changed the fuse, connected just inverter board and main relay to main board - all good. Connected everything else - heard (probably pump) noise and the fuse blown.

Took another look inside the filter housing, there's a small hole with a spinning stuff inside. It was stuck. Played quite a lot with it to take out my baby's sock stuck there. Replaced the fuse, connected everything and boom - it turned on, everything looks good!

Gonna secure the board with a glue gun, connect the water supply and drain hose and try running a quick wash soon. I'll let you know if it manages to finish the program.

[mrsith]

I've been checking it before I took the board out (checked for short between the middle front pin and the lone leg in the back, as per instructions found elsewhere on this forum on how to check that particular IC).

There's another, 3 pin mosfet with heatsink a bit further away that I wasn't able to reach before, I'll check it as soon as I can.

Edit: looks fine to me. Do you know how can I reliably test top253pn? The multifunction pin stuff confuses me a bit.